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Thanks James, very helpful! I've taken measurements at a few points that are pretty close to the Bosch curve. I'll use that and monitor as you suggest.

Is anyone using an AiM display that has been configured for the factory temperature sensors used for the coolant gauge and oil temperature? (parts store link here) Apparently it's a very common sensor used by a number of different car manufacturers and made by several sensor companies under the part number MD091056, but no one seems to publish any of the data. I've already checked with both US and UK AiM support, and a few Caterham specialists, without success. When testing the resistance output at a few temperatures between freezing and boiling, it became clear this is not a linear output, so having the actual resistance curve is needed to ensure any accuracy for my oil temp readings. Thanks, John

The fuse box is the factory version that normally sits sideways under the scuttle, but is rotated 90 degrees, then inserted into a 3D printed case that protrudes into the engine bay. Here are another couple of photos, but I don't want to derail this thread.

Yes, because I put it there :) I am using a Freewheel wireless steering wheel button system that has it's own native flasher relay with user adjustable auto canceling and flasher rate. That jumper gets a redundant relay out of the way and allows things to function correctly. -John

Looking at the diagrams in #5 and #6, am I correct that is the order when looking at the fuse box from the front? If so, the relays in my 2022 420R are wired in the reverse order. In the picture below, from left to right, #2 is the fuel pump, I'm pretty sure #3 is the starter, and #5 (with the jumper wire) is the flasher. I haven't traced the others. I wonder if the fuse boxes are hand assembled at the factory and some assemblers use the wiring diagram as a suggestion rather than a mandate?

I'm not sure if you're asking do they sell directly to consumers, supply directly to Caterham, or supplied the data directly to me, so I'll answer all three :-) I spoke with the person at Variohm who manages the Caterham account, so data is from the source; they have a specific supply contract for a custom sensor with Caterham; and it doesn't appear that they sell to the public but not sure if they sell that part to other resellers. The full part number which contains all the configuration data (output, range, thread size, wiring, etc) is EPT2100-B-00700-B-4-xxx (DT04-4P). The 00700 and xxx(DT04-4P) in the part number refer to the nonstandard aspects of the configuration. -John

I thought I'd circle back with the information in case anyone runs into this in the future, The sensor supplied by Variohm is the EPT2100 series but it is a special configuration for Caterham not listed on that sensor's product sheet. It has a linear output of 0.1-5v and a range of 0-7 bar, meaning it outputs 0.1v at 0 bar, 2.45v at 3.5 bar and 5v at 7 bar. -John

Thanks folks, that helps a lot!

I'm referring to the standard sensor that Caterham uses in all Duratec and Sigma powered cars. It's a Variohm Eurosensor, but I don't have the part number given the issue with the label. https://caterhamparts.co.uk/senders/3896-oil-pressure-sender-s3-sv-csr-including-loom.html Thanks, John

I'm hoping someone has installed an AiM display using the factory Variohm oil pressure sensor and can offer some guidance. My sensor arrived with a damaged label, making the model number unreadable. Consequently I can't track down the sensor information and configure the AiM to display correct values. Does anyone either have the calibration information or the Variohm part number? Thanks, John

According to info I copied from an old Cosworth catalog, lift for both cams is 9.5mm (0.374"). Duration for intake is 256 and exhaust is 246, however both are listed as 216 deg @ 0.050" -John

That looks like the Ford factory coil-on-plug connector. Emerald carries these and could probably advise on a crimping tool that will work. https://www.emeraldm3d.com/connectors/ford-duratec-coil-on-plug-2-pin-connector.html -John

A clarification on the dyno plot shown in #4 and linked in #3. That is the plot from my old engine. Although it has 420 cams, it has a different exhaust (4-2-1 with very long secondaries) and 45mm Jenveys. I suspect the shape of a 420 engine as fitted to a stock Caterham will be shaped slightly differently. BTW those are rear wheel numbers from a Mustang dyno. -John

I put the XAS FF on my Elan 4 years ago and my experience was the opposite of jbcollier's. Expensive, yes. And they do require tubes, but the tire is brilliant. Very sticky, great feel, and no balance issues. I will repeat when it is time for replacement. jbcollier, when you say they were "vintage re-pops made in India" from 10 years ago, were they actually Michelin branded tires or were they made by another company using that tread pattern? My understanding is the XAS is made Tigar in Serbia which is owned by Michelin. -John

Thanks guys. My understanding is that the current 420R measurements are 1.75" and 2.5", and I've been told both the R500 and 620R are bigger but it's unclear if those two are the same size. Based on the above, it looks like the primaries are bigger for the more powerful versions as expected, but the rear collector output/silencer are the same size at 2.5" (unless the old R400 used a larger exhaust than the later 420). That's a little surprising given the 310hp of the 620R. I expected 2.75" - 3" to support that power level. I'll keep digging, but welcome any additional input.

Does anyone happen to know the tubing diameter used for the 620R exhaust? I'm looking for the diameters of both the primaries and the rear of the collector feeding into the silencer. Thanks, John

Mazda has a forged crank available for the 2.3L that was used in their turbo versions. So equipped and with forged rods and pistons, a 2.3L can safely spin about as high as a 2.0L using forged rods and pistons but with the standard crank. Choosing between the two really comes down to your preferences for the shape and height of the torque curve. Assuming you are building the engine for 250+ hp, if you frequently like to short shift and use torque to get around, you might be happier with the larger engine. However, if you like to wring the engine to redline at every opportunity and don't mind having to work for it, then you might prefer the 2.0L. Another option is a 2.4L Duratec based on an Esslinger short block.(actually 2344cc vs. 2261cc for the 2.3L) It uses the 2.5L block that is slightly over bored, a forged 2.3L Mazda crank, and Esslinger's custom long rods and pistons. As configured, it's safe to over 8500rpm. You could use either the 2.3L head, or the even better flowing 2.5L head, although the latter requires VVT delete for bonnet clearance, and different throttle bodies as the shape of the intake ports are very different.

It's not a issue to run wasted spark on a Duratec. The coolant manifold that attaches to the back of the head is designed to take the wasted spark coil pack used in the earlier Duratecs. However, I would take a closer look at the capability of the Omex to make sure it has a good feature set that will support future plans. Things like data logging, multiple map selection,closed-loop self mapping, knock control, tractio control, and cam sensor input for COP and sequential injection are all nice things to have. Given you will likely need to buy or build a new engine harness, selecting the right ECU now will save you headaches down the road. One big decision you'll face is cam selection. I agonized over this as I didn't want to sacrifice too much low end. I was going from Kent DTEC10s, which are essentially the same as used in the 420 and have a very wide power band. After much deliberation, I went with the DTEC20s and am happy with that choice. Still sufficient torque below 3000rpm, but pulls strongly until 8100rpm when the rev limiter kicks in. My engine's peak power is held back by the exhaust which was originally sized for the DTEC10 cams. On the dyno, horsepower is perfectly flat from 6700-8100rpm when we stopped. I know someone in the UK with the same cams and pistons, similar head work and a larger exhaust whose dyno plot mirrors mine until 6700 when his continues to climb another 15hp to 240hp. Regarding heads, you may need some flow improvements or a head swap to meet your 250hp goal. The 2.0L Duratecs in the US (and I believe Canada) all have a more restrictive head than the 2004 and later 2.3L. SBD's site talks about the 2008 and later 2.0L heads being higher flow, but based on casting numbers, that head was not offered in the US on the 2.0L. However, it does appear to be the same as those later 2.3L heads, which are also referred to as high-port. I ran into a number of issues tracking down parts during my rebuild, so it may save you some headaches to read through my build thread on USA7s to grab obscure part numbers you may need. Feel free to PM me here or on USA7s if you have questions along the way. https://usa7s.net/ips/topic/12467-20l-duratec-rebuild/ -John

Unfortunately, Caterham doesn't mount the O2 sensor in an optimal position for longevity. The various aftermarket WBO2 controller manufacturers and Bosch all recommend positioning it at least 10% above horizontal to avoid moisture generated during cold start up from pooling on the sensor. In contrast, Caterham places it below horizontal. For my upcoming build, I plan to have the sensor mount relocated to address this. This doc is a good read on sensor mounting best practices: https://wbo2.com/lsu/LsuInstal.pdf

Although the oil pump is different internally, based on recent first-hand experience, the factory sprocket and chain assembly fit with no alterations. One caveat. Assuming this is an older dry sump, it might be worth calling Raceline to confirm there is nothing unique to that version. I ran into an issue when rebuilding another Duratec with an early Raceline wert sump. We discovered they made some design tweaks over the years, so some of the maintenance parts they initially provided did not fit.

I used an Innovate for years with my Emerald, but switched to the AEM X-Series as part of an engine upgrade 2 years ago. Reviews seemed more consistently positive and I did find some testing showing that it reacts more quickly. I can't confirm it's better, but I've been pleased with it thus far and purchased a second AEM for my new project. -John

Hmm... Ignore that last comment about 2.0L and 2.3L timing covers. I was just looking at a Mazda part number (L3N5-10-500C) and it shows that it fits 2.0L and 2.3L. -John

Not sure how much this will help in UK searches, but for US cars, the 2.3L in the 2003-2007 Ford Focus used part number: 2L8Z-6019-AA. The 2.3L is about 13mm taller than the 2.0L and they use the same head, so I suspect timing cover height may differ between the two engines. -John

I don't want to sidetrack this thread, but I'm considering several options, including converting the indicator to a combination sidelight/indicator with the DRL in the headlight. That will require modifying the loom, but I am already doing that for my non-standard dash. The simplest option is keeping that portion of the Caterham wiring stock and adding dedicated (and small) DRLs behind the grill that are wired with a relay to come on with the ignition and turn off when the sidelights are activated. For that to work, it needs to look good (to me) and offer least as much brightness as the dipped beams. The kit won't be here for several months, so lots of time to figure this out. -John

Thanks Neil, I appreciate it. I'd like to use a proper DRL setup on the new build rather than continue to manually switch the dipped beams on/off for every drive. I'm considering both these lights and small standalone units behind the grill. -John